Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

core/modules/contact/src/ContactMessageAccessControlHandler.php

@@ -0,0 +1,27 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\contact\ContactMessageAccessControlHandler.
+ */
+
+namespace Drupal\contact;
+
+use Drupal\Core\Access\AccessResult;
+use Drupal\Core\Entity\EntityAccessControlHandler;
+use Drupal\Core\Session\AccountInterface;
+
+/**
+ * Defines the access control handler for the message form entity type.
+ *
+ * @see \Drupal\contact\Entity\Message.
+ */
+class ContactMessageAccessControlHandler extends EntityAccessControlHandler {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function checkCreateAccess(AccountInterface $account, array $context, $entity_bundle = NULL) {
+    return AccessResult::allowedIfHasPermission($account, 'access site-wide contact form');
+  }
+}